Microbial transformation of ginsenoside-Rg1 by Absidia coerulea and the reversal activity of the metabolites towards multi-drug resistant tumor cells

Biotransformation of ginsenoside-Rg1 (1) by the fungus Absidia coerulea AS 3.2462 yielded five metabolites (2− 6). On the basis of spectroscopic data analyses, the metabolites were identified as ginsenoside-F1 (2), 6α,12β-dihydroxydammar-3-one-20(S)-O-β-D-glucopyranoside (3), 3-oxo-20(S)-protopanaxatriol (4), 3-oxo-7β-hydroxy-20(S)-protopanaxatriol (5), and 3-oxo-7β,15α-dihydroxy-20(S)-protopanaxatriol (6), respectively. Among them, 5 and 6 are new compounds. These results indicated that Absidia coerulea AS 3.2462 could catalyze the specific C-3 dehydrogenation of derivatives of ginsenoside-Rg1, as well as hydroxylation at the 7β and 15α positions. Metabolites 2, 4 and 5 exhibited moderate reversal activity towards A549/taxol MDR tumor cells in vitro.

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